This invention relates to a method for processing a medium, an image processing apparatus, for example such as a facsimile machine, and a photocopier, and a printer apparatus.
Conventionally, with a printer apparatus such as an impact dot printer, a ribbon mask for preventing a paper from staining is arranged between an ink ribbon situated on a front end of a print head and the paper as a medium, and ink from the ink ribbon is transferred through a hole formed at the ribbon mask to the paper.
With the conventional printer apparatus, however, a corner portion of the paper slides into the hole of the ribbon mask where printing operation is made from an upper end portion of the paper, so that obstructions such as a dog-eared paper, a paper travel jam, or spacing error may occur. Where the hole itself of the ribbon mask receives damages, rubbing of the ink ribbon or the damaged ribbon mask against the paper occurs during the subsequent printing operation, so that print quality may be deteriorated.
FIG. 2 is a plan view showing operation of medium conveyance according to the conventional printer apparatus; FIG. 3 is a side view showing the operation of the medium conveyance according to the conventional printer apparatus; FIG. 4 is a view showing a curl of the medium according to the conventional printer apparatus.
In drawings, numeral 41 is the paper as the medium, and during the printing operation, the paper 41, with the printer apparatus, is supplied from a paper supply opening, not shown, at a front side of a delivery route (a right side in FIG. 3), and passes over a table 45 to detect the setting by a table sensor 34. The paper 41, subsequently, is conveyed through a paper guide 42 on an upstream side by means of rotating a feed roller 44. At this moment, a skew sensor 33 judges as to whether the upper end of the paper 41 is horizontally supplied, and where the upper end of the paper 41 is horizontally supplied, the paper is further conveyed onto a platen 46. It is to be noted that the skew sensors and the table sensors are respectively arranged in a plural number.
A paper width sensor 32 arranged above the platen 46 confirms a position of the paper 41 by means of detecting left and right ends of the paper 41, and when the position of the paper 41 is confirmed, print data are printed by the print head 21. The printed paper 41 is conveyed to the paper guide 43 on a downstream side and is discharged from a discharge opening, not shown, at a back side of the delivery route (a left side in FIG. 3).
Herein, where the printing operation is made from the upper end portion of the paper 41, the corner portion of the paper 41 slides into the hole of the ribbon mask, not shown, so that there is a problem that obstructions such as the dog-eared paper, the paper travel jam, or spacing error may occur. Another problem exists such that where the hole itself of the ribbon mask receives damages, rubbing of the ink ribbon or the damaged ribbon mask against the paper 41 occurs during the subsequent printing operation, so that the print quality deteriorates.
The problems like the above tend to be more outstanding especially where the front end of the paper 41, as shown in FIG. 4, is curled (curved) upward. FIG. 4 (a) shows a large curling state, and FIG. 4(b) shows a small curling state. Additionally, where the front end of the paper 41 is curled, while the paper 41 is conveyed, as shown in FIG. 3, the front end of the paper 41 engages with the front end of the paper guide 43 arranged on the downstream side with respect to a printing position in entering into the above paper guide 43 on the downstream side, so that there has been such a problem that the paper travel jam easily occurs. Furthermore, with the printer apparatus having the paper width sensor 32 serving for a paper width detection function, when the paper width is detected, a left end position of the paper 41 cannot be accurately detected because of the curl of the front end of the paper 41, so that such a problem may occur that a print format becomes misaligned during the subsequent printing operation.
To solve the aforementioned problems, a printer apparatus has been proposed, e.g., such as described in Japanese Patent Application Publication No. JA-5-124282, wherein one paper guide is arranged on the upstream and the downstream sides respectively with respect to the printing position, and further, a paper holding plate is arranged between two paper guides for controlling the paper from above, and thereby preventing front end and the distal end of the paper from curling.
With the above described conventional printer apparatus, however, the structure becomes complicated because particular machinery such as the paper holding plate is equipped, so that a whole printer apparatus costs so greatly.
It is an object of this invention to solve the aforementioned problems of the conventional printer apparatus and to provide a medium detecting method, an image processing apparatus, and a printer apparatus for detecting folding of the medium by detecting the medium width at first and second positions to make printing suitably corresponding to folding of the medium.